How to reduce the serialize deserialize time in FastDDS 2.6.7

[Syamkamalnadhc]

I am using FastDDS 2.6.7 with ROS2-Humble and I need to optimize the performance, I put performance logs in FastDDS and observed ~300ms delay across the serialize and ~500ms deserialize when sending 1gb data. as per my understanding FastCDR module is handling the serialization process and i need to know are there any tunable configurations to reduce the delay.

[JesusPoderoso]

Hi @Syamkamalnadhc, thanks for using Fast DDS.
The serialization (and deserialization) process can be avoided using loan mechanism. Also, if your data type and your deployment meet these requirements, the use of zero-copy delivery mechanism may be of interest to improve the performance of the communication and reduce the number of copies performed.

[Syamkamalnadhc]

Is the UDP transport supports Loan mechanism?
I got an error "[rclcpp]: Currently used middleware can't loan messages. Local allocator will be used." when using UDPv4 and i did not get this message with SHM transport

[JesusPoderoso]

Humble version requires both data-sharing enabled and plain type to use loans, meanwhile Jazzy version and Iron version just the type to be plain.
Sorry for the inconvenience @Syamkamalnadhc.

[arunjs-dev]

Hi @JesusPoderoso, thank you for your confirmation.
Could you please provide an information about why humble version has such a limitation but not for Jazzy & Iron?

[JesusPoderoso]

Hi @arunjs-dev, that decision was taken by the rmw maintainers, and it is out of the eProsima Fast DDS scope.